Gas turbine engines in helicopter propulsion applications, for example, are protected against ingestion of airborne debris by inertial type inlet particle separators. Such separators mount on the engine upstream of the usual annular compressor entry and have flowpath defining walls which change the direction of the airflow through the separator to disassociate debris from the air. To the end of avoiding ice deposits on the flowpath defining walls of the separator, it is known to fashion internal heating air channels in the separator which circulate hot compressed air from the engine behind the flowpath defining walls of the separator. To the extent that heat is transferred from the air in the heating air channels to portions of the separator not susceptible to icing, such as to internal structural walls or to portions of the flowpath defining walls not frontally exposed to the airstream, engine efficiency is sacrificed. An inlet particle separator according to this invention incorporates novel internal heating air channels which minimize consumption of hot compressed air from the engine by minimizing heat transfer to parts of the separator not susceptible to icing and maximizing heat transfer to patches or sections of the flowpath defining walls susceptible to icing.